This invention relates to X-ray apparatus which is useful for general X-ray diagnostic work but which has the capability of being quickly converted to a form useful for making specialized vascular studies, such as arteriographic studies of the heart.
Prior art apparatus for making general purpose X-ray examination, as well as specialized arteriographic studies of the heart, have included a patient supporting table, an X-ray source on one side of the patient supporting table, and an X-ray imaging system on the other side, with the X-ray source and the imaging system so mounted that the central X-ray beam remains directed at the image plane for various angles at which the heart is to be viewed.
A typical prior art X-ray imaging system includes an electronic image amplifying tube whose function is to convert an X-ray image into a small bright optical image that appears on a phosphorescent disc. Mounted above the disc is a television camera which is used to display the converted X-ray image on a television monitor.
In the present application, the term image amplifier will, for convenience, be used to designate the image amplifier housing and all of its contents, including the image intensifier, the television camera, and any other devices which may be contained in or affiliated with the image intensifier system. In a typical case, the image amplifier is mounted above the cradle and table top on which the patient is supported, with the X-ray tube being located below the patient-supporting cradle and table top.
If the patient to be examined is placed in a horizontal cradle supported on a horizontal table top, the X-ray beam will pass vertically through the patient to the image intensifier, and important blood vessels which are disposed with their axes perpendicular to the viewing plane will be difficult to observe and study. Moreover, certain blood vessels in the heart may be concealed by other blood vessels so that it will be difficult to observe and study them. One solution proposed by the prior art to this problem has been to angulate the X-ray source and the image intensifier jointly. Another proposal by the prior art has been to support the patient in a cradle and on a table which is capable of being rotated and angulated relative to the X-ray beam, thereby to enable viewing of the heart from various angles. In yet other prior art designs, the X-ray source and image intensifier are angulated and the patient is also supported for limited rotational movement.
In some prior art apparatus of the foregoing types, the patient is supported on a table and the X-ray source and the image intensifier are mounted in free space. Such an arrangement is subject to a major disadvantage in that the operator is not shielded from stray and secondary X-ray radiation.
More recently, improved apparatus directed to the foregoing problem has been provided. Such apparatus is disclosed in Bernstein et al U.S. Pat. Nos. 4,024,401 and 4,024,403, each assigned to General Electric Company. Bernstein et al U.S. Pat. No. 4,024,401 discloses a floor mounted enclosure, a patient supporting table on the enclosure, an X-ray tube casing mounted in the enclosure for angulating movement about a fixed axis, an X-ray image-intensifier assembly supported above the table for angulating movement, and an extensible-contractable optionally removable link arm for coupling the X-ray tube casing and the image-intensifier assembly to provide coordinate angulation of the X-ray tube relative to the image-intensifier assembly. It is to be particularly noted that in this prior art U.S. Pat. No. 4,024,401, the X-ray tube casing is angulated on a fixed pivot axis. A disadvantage of such construction is that it imposes an undue restriction upon the extent to which the system can be angulated without having the material surrounding the exit opening in the cabinet cut off an undesirably large part of the X-ray beam.